There has been considerable study of experience-dependent behavioral plasticity in different experimental systems, but little is known of how such plasticity occurs in the processing of sensory information, particularly with respect to light and vision. The objective of this proposal is to develop a new paradigm for the study of experience-dependent plasticity using the phototactic visual response of Drosophila melanogaster. We have devised a branching maze device that sorts flies according to wavelength or light/dark preference and phototactic walking behavior. We have also developed a conditioning paradigm that yields strong changes in light/dark preference, which can be precisely measured by performance in the maze. We seek support to further develop this conditioning paradigm and behavioral assay, to determine the phases of memory and how these are modulated by variation of the conditioning protocol. We will work towards localizing the neurons whose function is modulated to yield plasticity. We will construct an automated training and assay apparatus, which will be employed in a large-scale search for genes that play a role in this form of behavioral plasticity. In the longer term, we hope to develop this approach into an important experimental paradigm for the study of behavioral plasticity, to serve as a distinct parallel to ongoing work in olfactory behavioral plasticity, and to provide a new window on understanding the plasticity of visual system function and its behavioral consequences.